10 years ago I did some nice 4 min length animations, like 

http://www.main.artbeeweb.nl/?p=4003

4 CPU's (single core, single thread, 1.8GHz), over 3 weeks full time (24/7) rendering, in separate frame-images. Some frames took 20 hours each due to reflections. 

Rendering is fun :-) unless you're impatient.

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Usually I'm wrong. But to be effective and efficient, I don't need to be correct or accurate.

visit www.aRtBeeWeb.nl (works) or Missing Manuals (tutorials & reviews) - both need an update though